Radio Frequency Integrated Circuit (RFIC) networks can utilize impedance matching circuits to interface different sub-sections within the RFIC network. The impedance matching circuits may be used to improve power transfer between network sub-sections, and/or mitigate signal reflections occurring between the sub-sections' electrical boundaries. Fabricating the impedance matching circuits directly on the RFIC substrate itself may be beneficial for driving cost reduction and improving packaging efficiency.
Tuning matching networks to improve performance can present challenges to the circuit designer. Because parameters of the various circuit elements (e.g., inductors, capacitors, etc.) depend upon many factors, performance of the impedance matching circuit can be difficult to predict. Conventionally, in order to achieve sufficient accuracy for impedance matching, tuning the impedance matching networks may utilize iterative, trial-and-error techniques. One conventional approach may involve making an initial guess with a particular on-chip circuit element, then measuring the result to determine the circuit's effectiveness. If the circuit's performance is unsatisfactory, a circuit element in the impedance matching circuit can be substituted with another having a different value. This process may be repeated unit the RF network performs adequately.
The substitution of the circuit element may be performed by physically removing the old circuit element and replacing it with a new one. However, this approach may not be the most practical as circuit elements placed on the die of the integrated circuit can be difficult to physically replace. Physical replacement of the circuit elements may involve costly metal spins of the integrated circuit. Metal spins are additional tapeouts (e.g., sending the design to manufacturing) wherein the metal layers of the circuit are altered, but the silicon layers are left unchanged.
A more cost effective approach may involve placing/fabricating a plurality of circuit elements (i.e., a “bank” of circuit elements) on the integrated circuit, and selecting one or more circuit elements from the plurality to determine which provides the best performance.
Impedance matching circuits commonly utilize inductors to achieve a resonance effect at a desired frequency. It therefore may be desirable to alter the inductance value of the inductor in order to tune the impedance matching circuit. However, inductors fabricated using integrated circuit techniques can occupy a significant amount of space on the integrated circuit die (e.g., typically 300 um by 300 um or more). Therefore, it may be impractical to implement an inductor bank for altering an inductor value to facilitate the tuning of the impedance matching circuit.
Accordingly, there is a need for RFIC impedance matching circuits which may be easily and economically tuned for improved performance.